Replies

Great job of digging out that landing profile info, snope...

As far as the yaw/roll/drag terms, I have to admit the way these have been thrown around has bothered me all week. From the first briefing, it appeared to me all the data which had been discussed described compensation by the autopilot for increased drag, not to counter roll. I've been ignoring that detail due to it being a bit nit-picking, but I'll concur with your opinions here. By the way, I'm a former AF pilot.

As far as "being within nominal parameters", that simply means the normal control systems could handle the changes, not that they reflected a typical Shuttle reentry, I believe. In other words, I took that statement to mean that the autopilot had no trouble trimming the Shuttle to the attitude it was directing. I also believe that statement was made before they had analyzed data which apparently shows the yaw thrusters were fired, and I'm NOT sure that IS normal.

My final comment here is that I believe the S-turns are made not so much to lose altitude, as to dissipate energy by loading the plane, as well as to maintain a desired altitude/distance from touchdown profile. The turns they use would be pretty radical for a commercial-type aircraft, but the 60-80 degree banks are routine for more roubust AF aircraft, and I could envision using such a technique (arrive high over the field, and hard "S"s/circles to bring 'er down) were I to be making an engine out attempt to land at an emergency field.

OK, I finally figured it out. The Columbia had completed it's roll to the right, and was just entering it's first roll to the left [roll reversal] when the problems first started to manifest themselves.

I think this is significant, since if the leading edge of the left wing had been damaged (either during launch, or by ice from the urine-dump port), it would have been out of the wind during the initial roll to the right.

As the shuttle reversed and rolled to the left, the left wing would be poining at the ground and toward the forward path of the Columbia - IOW, into the wind.

I found this at a NASA website and thought it was concise [Link]:

Deorbit burn occured at 8:15 a.m. EST (1315 GMT) for a planned landing on KSC Runway 33. At approximately 8:52 a.m. EST, Columbia was crossing over the coast of California and entering Roll Reversal #1. Columbia was traveling at Mach 20.9 and 224,390 ft (MET 15 days 22 hours 17 min 50 seconds)
At 8:52:20 EST, Columbia's Left Main Gear Brake Line Temp D in the left wheel well showed an off nominal temperature rise (2 degrees/min) followed by an off nominal temperature rise in Brake Line Temp A (6 degrees/min) at 8:52:39 (13:52:39 GMT) and Temp C (5 degrees/min) at 8:52:48. At 13:52:59 GMT, flight controllers saw a loss of sensor data (offscale low) from the Left Inbord Elevon Lower Skin Temp followed by a loss of sensor data from the Hydraulic System 3 Left Outboard Elevon Actuator Return Line Temp (13:53:10), Hydraulic System 1 Left Inboard Elevon Actuator Return Line Temp (13:53:11), Hydraulic system 1 Left Outboard Elevon Actuator Return Line Temp (13:53:31), Hydraulic System 2 Left Inboard Elevon Actuator Return Line Temp (8:53:36). Wires from these sensors are routed inside the wing from the orbiter midbody, in front of the main landing gear towards the leading edge and then back to the sensor locations near the trailing edge of the wing.
At 8:54 a.m. EST, while the orbiter was crossing over Eastern California, sensors indicated there was an increase in temperature in the left wheel well and Mid Fuselage. The Left Main Gear Brake Line Temp B showed an off nominal temperature rise (6 degrees/min) (8:54:13) followed by an off nominal rise (6 degrees/min) of the Mid Fuselage Left Body Line (X-axis=1215) Temperature (8:54:22), Left Main Gear Strut Actuator Temp (7 degrees/min) (8:54:27), Left Main Gear Uplock Actuator Unlock Line Temp (4 degrees/min) (13:54:36) and the System 3 Left Hand Forward Brake Switch valve Return line Temp (5 degrees/min) (13:55:23). Over a 5 minute period, Columbia's left side increased 60 degrees F while the right side increased only 15 degrees F during the same time. During this time, the inside of the Payload Bay was normal.
Shortly before 8:58 a.m. EST, while the orbiter was over New Mexico, sensors indicated an increase in drag on the left side and the flight control systems were automatically compensating. Then the Main Landing Gear Left Outboard Wheel Temperature Sensor went offline (13:55:35) followed by the Left Upper and Lower Wing Skin Temp Sensor (13:56:20). At 13:57:54, the System 2 Left Hand Aft Brake Switch Valve Return Temp increased in temperature (14 degrees/min) and the Main Landing Gear Left Hand Outboard and Inboard Tire Pressure 1&2 (13:58:33/13:58:39) and Wheel Temperature (13:58:35) goes offline (offscale low).
At 8:59 a.m. the Tire pressure sensor caused an onboard alert that was acknowledged by the crew. Communication with the crew and loss of data occured shortly after while Columbia was at a Mission Elapsed Time (MET) of 15 days 22 hours 20 minutes 22 seconds. The vehicle broke up while traveling at 12,500 mph (Mach 18.3) at an altitude of 207,135ft over East Central Texas resulting in the loss of both vehicle and crew. (Reference: JSC Ron Dittemore Post flight Technical News Conference 2/1/03, 2/2/03 and 2/7/03 3:30 pm CST).